Engine Control Module (ECM)

IMPORTANT: Never clear the Diagnostic Trouble Codes (DTCs) unless you are instructed to do so by the diagnostic procedure. Clearing the DTCs will erase the Freeze Frame buffer. Clearing the DTCs may also reset the Maintenance Inspection flags that are used for emission testing stations. If for any reason the ECM memory is cleared (Battery disconnect, using a scan tool or charging system malfunction), the diagnostics must be run in order to reset the flags.

Use a scan tool in order to read the diagnostic trouble codes.
Since the ECM can have a failure which may affect only one circuit, following the diagnostic procedures in this section will determine which circuit has a problem and where the problem is located.
If a diagnostic table indicates that the ECM connections or the ECM is the cause of a problem and the ECM is replaced, but does not correct the problem, one of the following conditions may be the reason:

There is a problem with the ECM terminal connections
The diagnostic table may instruct the technician to check the ECM connections. You may have to remove the terminals from the connector in order to check the terminals properly.

The EEPROM calibration/software is not correct
Unlike the PROM that was used in the past applications, the EEPROM is not replaceable. If you replace the ECM, make sure that the new ECM's software/calibration is correct for the vehicle and is the most recent version. Special equipment as well as the correct program and calibration for the vehicle is required in order to re-program the ECM.

The problem is intermittent
This means that the problem is not present at the time the system is being checked. In this case, refer to the Symptoms portion of the manual and make a careful physical inspection of all of the portions of the system involved.

Shorted solenoid, relay coil, or harness
The solenoids and relays are turned on and off by the ECM by using the internal electronic switches called drivers. A shorted solenoid, relay coil, or harness will not damage the ECM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast and accurate means of checking for a shorted coil or a short to battery voltage.